Between 300,000 and 400,000 deaths per year in the United States result from cardiac arrest. Further, most cardiac arrest deaths occur outside the hospital. In fact, current out-of-hospital survival rates are one to five percent (1-5%). In 1999 and 2000, for example, cardiac arrest caused 815 of 6,339 workplace fatalities reported to the Occupational Health and Safety Administration (OSHA). Abnormal heart rhythms cause cardiac arrest, and ventricular fibrillation (VF or V-Fib) is the most common of these abnormal rhythms. VF is a heart condition in which the heart quivers instead of mechanically pumping blood throughout the body and thus causes the heart to stop circulating blood. The most effective treatment for VF is administering CPR followed by use of a defibrillator as soon as it is available. Treatment of VF with immediate electronic defibrillation may increase survival to more than ninety percent (90%). But with each minute of delay in defibrillation, ten percent (10%) fewer victims survive.
An automated external defibrillator (AED) may be designed to allow anyone to use the defibrillator regardless of whether the user has been formally trained on its operations. AEDs may accomplish this through the use of voice instructions, pictures, and prompts, for example. An AED may only deliver a shock if indicated, and AEDs may be nonhazardous when used correctly. AEDs may improve survival after an out-of-hospital cardiac arrest because use of AEDs may reduce the critical time for treatment. That is, less time between the cardiac incident and defibrillation may improve the victim's chances of survival. For example, defibrillation within three minutes of sudden cardiac arrest (SCA) increases the chances of the SCA victim's survival to seventy percent (70%). Further, defibrillation within one minute of collapse raises the survival rate to ninety percent (90%). Laws and regulations may recommend or require AEDs in various locations (e.g., a workplace), but defibrillation may be delayed as a result of the time it takes to locate a nearby fixed AED. In addition, many locations do not have available AEDs. Frequently, calling emergency medical services (EMS) is necessary, but the wait for first responders may take too long. For example, the average call-to-shock time in a typical community is nine minutes. Time is crucial in an SCA, and there may only be minutes between life and death. CPR may only buy a little more time, potentially giving the victim a small amount of extra time until a defibrillator arrives. However, SCA ultimately requires a shock to restore a normal heart rhythm. As a result, CPR and heart saving training also may include AED training. An AED does not restart the heart or fix a “flat line,” however, because a flat line represents that there is no heart electrical activity at all. That is, a flat line often represents clinical death because it is rare to recover from a flat line rhythm. Consequently, an AED attempts to correct the electrical system of the heart that is malfunctioning rather than to jump start it. If an AED recognizes a “flat line,” it may indicate that no shock is advised and instruct the user to resume CPR because shocking a flat line does not benefit the victim.
In the workplace, thirteen percent (13%) of all workplace fatalities stem from SCA, which is the leading cause of death in the United States. For example, death from SCA in the United States is 96 times more likely than death from fire. Nevertheless, many entities have a sufficient number of fire extinguishers in place to protect their employees, customers, and visitors but nevertheless severely lack installed AEDs. However, having AEDs readily available in the workplace, along with training and installation policies and programs, may mean the difference between life and death. The American Heart Association (AHA) strongly supports having AEDs in public areas such as sports arenas, office complexes, schools, doctors' offices, shopping malls, airports, and other public places. The AHA also advocates that all police, fire, and rescue vehicles be equipped with an AED. Availability of AEDs may be important because use of an AED is an immediate action that may be required to save any victim undergoing an SCA. An AED may be operated successfully by any bystander, who does not need to be medically trained, in any emergent situation, such as a public place, school, office, and communities alike. In fact, victims of SCA who are treated with AEDs by bystanders are much more likely to survive.
SCA takes the lives of 400,000 people per year. During SCA, the heart's normal heart rhythm suddenly may become chaotic. The heart is no longer able to pump blood effectively, and the victim may collapse, stop breathing, become unresponsive, and have no detectable pulse. SCA may strike anyone at any time, including people of a variety of ages and fitness levels. That is, children, teenagers, athletes, and elderly individuals all may experience SCA. Although the risk of SCA increases with age and with a history of heart problems, a large percentage of SCA victims are people with no known risk factors. Further, SCA is different from a heart attack, i.e., a myocardial infarction. In simple terms, SCA is an electrical problem, whereas a heart attack is a “plumbing” problem, as described in the table illustrated in FIG. 20, for example. In some cases a heart attack, which itself may not be fatal, actually may trigger SCA. The globally recognized treatment for SCA is defibrillation, and it is the only treatment proven to restore a normal heart rhythm. When used on a victim of SCA, an AED may be used to administer a lifesaving electric shock that restores the heart's rhythm to normal. But although AEDs may be designed to allow non-medical personnel to save lives, AED machines may not be installed everywhere and often take extra time to locate and bring to any emergency situation.
One study found that overall survival to hospital discharge from 13,769 cardiac arrests was seven percent (7%). However the survival rate increased to nine percent (9%) for victims who received bystander CPR, twenty-four percent (24%) for those who had an AED applied before EMS personnel arrived, and thirty-eight percent (38%) for those who received an AED shock before EMS arrival. After adjusting for age, sex, bystander CPR, arrest location, EMS response time, witness status, initial rhythm, and study site, the study found that AED application was associated with a greater likelihood of survival (OR 1.75, 95% CI 1.23 to 1.50). More specifically, to assess the clinical and public health impact of investment in AEDs, which sell at a rate of about 200,000 per year, the study used data from the Resuscitation Outcomes Consortium (ROC), which encompasses 215 EMS agencies in seven sites in the United States and three in Canada. The ROC Epistry Cardiac Arrest registry records information on non-traumatic out-of-hospital cardiac arrests. The study analysis included 13,769 cardiac arrests that were not witnessed by EMS personnel. Of those, 2.1% had an AED applied before EMS arrival. That rate ranged from 1% to 7% between sites. The AED was applied by lay volunteers in 35% of the cases, by healthcare workers in 32%, by police in 26%, and by unknown bystanders in 7%. Survival was highest following an AED application by a lay volunteer (40%), followed by healthcare workers (16%) and police (13%), which demonstrates the greater importance of speed compared to training. In a post hoc analysis, absolute survival rates were higher in public sites (35% with AED application and 20% without) than in private locations (9% with AED application and 6% without). However, after multivariable adjustment there was no significant interaction between arrest location and survival (P=0.53). The researchers extrapolated their findings from the population served by the ROC, which was about 21 million people, to the combined population of the United States and Canada, which is about 330 million people, and estimated that AED application to victims of out-of-hospital cardiac arrest by bystanders saves about 474 lives per year.
AEDs may be nonhazardous to use by anyone who has been shown how to use an AED. In fact, some AEDs include voice guidance to guide a rescuer through the steps involved in saving someone, e.g., “apply pads to the victim's bare chest” and “press the red shock button.” In addition, the pads themselves may have pictures of where they should be placed. Furthermore, safeguards sometimes have been designed into AEDs to ensure that non-medical responders may not use the AED to shock someone who does not need a shock.
AEDs may come with a lithium battery pack, which may have 5- or 7-year lifespan, for example. If the AED is used frequently, however, the battery pack may have to be replaced more often. In addition, an AED may inform an end user when the battery pack needs to be replaced. Further, an electrode pad package may need to be replaced every two years. An AED may perform automatic self-checks on a daily basis to test its operational readiness. If anything is not fully functional, the unit may initiate an alert with a loud chirp and flash a red light to warn that service may be required.